1. Field of the Invention
The present invention relates to an apparatus for the maintenance of soil moisture at a specific moisture content. This invention relates more specifically to the maintenance of soil water content to preserve the foundations of houses and buildings such that they are not subject to the compressive forces of soil when the soil changes volume. Soil changes volume whenever it absorbs ground water. This is especially true when the soil is hydrated from a dessicated state.
2. Description of the Prior Art
The destruction of foundations by the expansion of soil has cost the homeowner literally billions of dollars in costly repairs. Ground soil becomes dry because of environmental conditions such as summer heat and dry air. However, when dry soil is exposed to rain, it absorbs and retains this water. In doing so, the soil expands and requires additional space to accommodate its new volume. Though the expansion is minute, the compressive forces of expanding soil can damage a stationary foundation.
The most damaging of soils is clay. It has the largest expansion volume change of most soils. Thus, when it expands, it exerts the highest forces upon a foundation even through the actual displacement of the soil is very small.
In order to alleviate the problem of foundation damage due to these forces, it is necessary to eliminate the forces exerted by the soil when it expands. One possible way to accomplish this task would be to keep the soil completely dry. However, keeping the soil dry is impractical. One would have to make sure tht the rain never reached the soil around the foundation. This task is both difficult and poses additional problems, especially if one wishes to place decorative shrubbery around the home. Without water, clearly the shrubbery cannot survive. Since it is not practical to keep the soil completely dry, the present invention has been devised.
The present invention keeps the soil at a constant level of moisture content. In this way, the soil cannot expand further, because it is already expanded to its fullest extent. When it rains, the soil cannot absorb additional moisture if it is already saturated with water.
In order to maintain a constant level of soil moisture, the soil must be continuously watered. U.S. Pat. No. 4,534,143 issued to Goines et. al. discloses such a watering device. In this patent, water is supplied to the soil surroundng a foundation in a continuous manner. However, seasonal changes will change the soil requirement for ground water. In a rainy season such as spring, the soil will require less water than in the summer when the soil is especially dry.
The existence of vegetation will also alter the requirements of soil moisture in a localized fashion. If a tree is present near a foundation, the roots will absorb more moisture from that area than if the tree were absent. Thus, there is a localized depletion of the soil moisture content. As a result, when it rains, the soil in that area will be susceptible to a greater amount of expansion than the soil that contains a larger amount of water. This expansion can put a localized stress on the foundation that can be more damaging than a constant stress over the entire foundation. This is true because the foundation will buckle at the point of higher stress than at the point of lower stress. As a result, the foundation is more likely to crack to a greater degree in this region than in the regions where the stress is continuous.
The Goines et. al. patent provides a partial solution to the problem. However, it discloses a device that provides a constant amount of water to the surrounding soil in all locations around the foundation. Although functional, this system creates an immediate problem. There is no control over the use of water. No matter the day or the season, the device provides the same amount of water to the ground soil. Thus, this invention wastes water when the soil does not need it. The present invention solves this problem by providing a method for controlling the amount of water introduced to the soil depending upon the needs of the soil given whatever environmental conditions.
Not only does the present invention provide water to the entire system on a demand basis, it also provides for a localized dispersion of water. This feature allows for an even dispersion of water around the foundation. Water can be supplied to those areas that are lacking such as those near plants and vegetation without wasting water on those areas sufficiently hydrated. The main focus of such a design is the conservation of water through its efficient management.
The present invention is additionally designed such that it can be installed both above ground and below ground. Above ground installation is particularly important when one is installing such a device to an existing home. Below ground installation is useful when the home is being built. A below ground system has the additional advantage of inconspicuousness.